Setting innerHTML vs. setting value with Javascript

value is for form elements, innerHTML if you want to set the content of any other element.
There's also innerText if you want to set the text content (you won't have to escape anything in there, but no HTML works in there)

Setting the value is normally used for input/form elements. innerHTML is normally used for div, span, td and similar elements.

Here is a link showing the use of ID.value: http://www.javascript-coder.com/javascript-form/javascript-form-value.phtml